White-bellied Go-away Bird
Corythaixoides leucogaster

Go-away Birds are kinds of Turaco. The name comes from their alarm call which is said to sound like "Go away!"
Like Turacos, they have high crests but, unlike Turacos, they are grey and white. The White-bellied Go-away Bird comes from Central and southern Africa.
It eats mainly fruit and berries. The male has a black beak and the female a yellowy-green beak.

As you go away, the length of the tail becomes clear -- well over the length of the rest of the bird.